Effect of adhesive materials on shear bond strength of a mineral trioxide aggregate

To compare the shear bond strength (SBS) and fractography between mineral trioxide aggregate (MTA) and glass-ionomer cement (GIC) or resin composite (RC) after varying MTA setting time intervals.

MTA was mixed and packed into standardized cavities (4 mm diameter x 3 mm depth) in acrylic blocks. RC with 37% H₃PO₄ and type 2 (etch and rinse) adhesive, or conventional GIC was bonded to the exposed MTA sample surfaces after 10-minute, 24-hour, 72-hour and 30-day MTA setting intervals (n = 10/group, eight groups). Samples were stored (37°C, 24 hours, 100% humidity) before SBS testing and statistical analysis (ANOVA, Tukey LSD, P < 0.05). Fractography was undertaken using stereomicroscopy for all samples and three random samples/group by using SEM.

Significant differences between all groups were found (P= 0.002). SBS of RC:MTA (Max 5.09 ± 1.79 MPa) was higher than the SBS of GIC:MTA (Max 3.74 ± 0.70 MPa) in 24-hour, 72-hour and 30-day groups except in the 10-minute MTA setting time groups, where SBS of GIC:MTA was higher. There was a significant effect of time on SBS of RC: MTA (P = 0.008) and no effect on SBS of GIC:MTA (P = 3.00). Fractography revealed mixed (adhesive/cohesive) failures in all groups; in RC:MTA groups there was a decrease in adhesive failure with time in contrast to the GIC:MTA groups.